The present invention relates to a radiography apparatus and a radiography method. More particularly, the present invention is concerned with a radiography apparatus and a radiography method which construct images of a subject according to projection data items of the subject produced by performing a main scan in which radiation is irradiated from a radiation tube to the subject and radiation transmitted by the subject is detected.
A radiography apparatus including an X-ray computed tomography (CT) apparatus reconstructs images of a subject's tomographic layer according to projection data items produced by scanning a subject with radiation. The radiography apparatus is widely adopted for medical application and industrial application.
In the radiography apparatus, for example, a blood flow examination called CT perfusion or angiography called CT angiography is performed using a contrast medium for the purpose of diagnosis of an ischemic disease in an encephalic region (refer to, for example, Patent Document 1 and Patent Document 2).
[Patent Document 1] Japanese Unexamined Patent Publication No. 2004-159983
[Patent Document 2] Japanese Unexamined Patent Publication No. 2005-6772
For CT perfusion or CT angiography, a scan is performed exclusively to each of CT perfusion and CT angiography in order to acquire data concerning a blood flow examination or data concerning images constructed through angiography.
Therefore, it may be hard to minimize an amount of a contrast medium or a patient dose. Moreover, since an examination lasts over a long period of time, it may be hard to improve diagnostic efficiency.